1 '  AciZ\Z'- ISS  ^g 

O,  E.  s.  LiBRAay.  Cop.  a  '' 

CONNECTICUT 


AGRICOLTDRAL  EXPERIMENT  SIATIOH 

NEW     HAVEN,    CONN. 


BULLETIN    155,   MAY,  1907. 


ENTOMOLOGICAL    SERIES,    No.    14. 

The  Elm  Leaf  Beetle 


CONTENTS. 

Page. 

The  elm  leaf  beetle 3 

History  and  distribution  in  America 3 

Life  history  and  habits 5 

Description 7 

Effect  upon  the  trees 8 

Food  plants      8 

Number  of  generations 9 

Natural  enemies 9 

Remedies 10 

Spraying  with  poison 10 

Destroying  the  pupae 12 

Destroying  the  adult  beetles 12 

Outfit  for  spraying  elm  trees 12 

Summary _ 13 


The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Con- 
necticut -who  apply  for  them,  and  to  others  as  far  as  the  editions 
permit. 


c^. 


no ,  ( S'S: 


CONNECTICDT   AGRICULTURAL  EIPERIMENT   STATION, 


BOARD   OF   CONTROL. 
His  Excellency,  Rollin   S.  Woodruff,  Ex  officio.  President. 

Prof.  H.  W.  Coxx   Middletown. 

Prof.  W.  H.  Brewer,  Secretary   New  Haven. 

B.  W.  Collins   Meriden. 

Charles  M.  Jarvis   Berlin. 

Edwin  Hoyt   New  Canaan. 

J.  H.  Webb Hamden. 

E.  H.  Jenkins,  Director  and  Treasurer New  Haven. 


STATION    STAFF. 

Chemists. 

Analytical  Laboratory. 

John  P.  Street,  M.Sc,  Chemist  in  charge. 

E.  :\Ionroe  Bailey,  M.S.  E.  J.  Shanley,  Ph.E. 

Kate  G.  Barber,  Ph.D.,  Microscopist. 

Laboratory  for  the  Study  of  Proteids. 
T.  B.  Osborne,  Ph.D.,  Chemist  in  Charge.        C.  A.  Brautlecht,  Ph.B. 

Botanist. 
G.  P.  Clinton,  S.D. 

Entomologist. 
W.  E.  Britton,  Ph.D. 

Assistant  in  Entomology. 
B.  H.  Walden,  B.Agr. 

Forester. 
Austin  F.  Hawes,  I\I.F. 

Agronomist. 
Edward  JNI.  East,  M.S. 

Stenographers  and  Clerks. 

Miss  V.  E.  Cole. 
Miss  L.  M.  Brautlecht. 
Miss  E.  B.  Whittlesey. 

In  charge  of  Buildings  a)td  Grounds. 
William  Veitch. 

Laboratory  Helper. 
Hugo  Lange. 

Sampling  Agent. 
V.  L.  Churchill,  New  Haven. 


The  Elm  Leaf  Beetle. 


BY 


W.   E.   BRITTON, 

state  Entoiiiotozist. 


Twelve  years  ago  an  account  of  this  insect  was  published 
by  this  Station  in  Bulletin  No.  121,  which  has  for  some  time 
been  out  of  print.  Since  then  only  a  few  scattered  notes  have 
appeared  in  the  bulletins  and  reports.  The  object  of  the  pres- 
ent paper  is  to  place  in  the  hands  of  the  people  of  Connecticut 
a  fairly  complete  and  comprehensive  account  of  the  elm  leaf 
beetle  with  up-to-date  remedies  and  methods  of  treatment. 
There  is  a  constant  demand  for  such  information  from  public 
school  teachers,  members  of  village  improvement  societies,  and 
men  employed  in  the  street  and  park  departments  of  our  cities 
and  towns,  as  well  as  from  private  individuals  who  desire  to 
give  the  best  care  to  trees  on  their  home  grounds. 

HISTORY  AND  DISTRIBUTION   IN   AMERICA. 

The  elm  leaf  beetle  was  introduced  into  this  country  probably 
more  than  seventy  years  ago.  In  its  native  countiy,  Europe, 
where  it  had  long  been  known,  it  had  from  time  to  time  caused 
serious  injury  in  Italy,  Austria,  and  the  southern  portions  of 
France  and  Germany.  In  Northern  Europe  the  insect  occurs 
sparingly,  but  can  hardly  be  called  a  pest.  Harris  states*  that 
the  elm  leaf  beetle  attacked  and  seriously  injured  the  elm  trees 
of  Baltimore,  Md.  in  1838  and  1839.  The  beetle  seemed  to 
spread  chiefly  northward,  though  slowly,  until  Southern  New 
England  was  reached  in  the  early  nineties,  and  much  damage 
done.  In  the  coast  towns  of  Connecticut  many  fine  old  elms, 
including  some  historic  trees,  were  killed  by  its  depredations. 


*  Insects  Injurious  to  Vegetation,  page  124. 


4  CONNECTICTT    i:X  I'I'.KI  M  i:.\'l"    STATtOX    UL'I.LHTIX     I  55. 

Stamford,  Xorwalk,  IJridi^eptjrt,  Stratford.  Milford  and  Xew 
Haven  especially  lost  many  noble  trees.  Later  the  inland  cities 
were  invaded,  and  the  elm  trees  ravaged.  In  Xew  Haven  the 
pest  was  perhaps  at  its  worst  in  1895  and  1896.  In  1896  many 
of  the  trees  on  the  older  streets  a1x)ut  the  center  of  the  city  were 
sprayed  with  poison  by  the  street  department.  The  following 
season  the  pest  was  less  serious,  and  continued  to  subside  until 
1901,    when    it    was    again    comparatively    destructive.     From 


Fig.   I. — Elm  leaves  showing  larvae  and  the   damage  whicli   they  do 
by  feeding  on  the  under  surface,  natural  size. 


1902  it  diminished  in  abundance  until  1906.  when  considerable 
damage  was  done  to  the  trees. 

So  far  as  is  known  the  distribution  of  this  insect  in  America 
is  confined  chiefly  to  the  lower  altitudes  of  Southern  Xew  Eng- 
land and  the  Alleghanian  region.  From  Ch.arlotte.  X'.  C 
its  southern  limit,  the  elm  leaf  beetle  now  extends  as  fnr  north 
as  Xorth  Conway,  Xew  Hampshire.  I'ji  t<>  tliis  time,  however, 
the  beetle  has  done  no  particular  daniaue  in  Xew  Hampshire. 
Regions  generally  infested  inchulc  the  whole  of  Massachusetts, 


THE   ELM   LEAF   BEETLE.  5 

Rhode  Island,  Connecticut,  southeastern  New  York,  New 
Jersey,  eastern  Pennsylvania,  Delaware,  Maryland  and  a  por- 
tion of  Kentucky,  though  isolated  outbreaks  have  occurred  in 
western  New  York,  Pennsylvania,  West  Virginia,  Ohio  and 
North  Carolina.  It  is  of  course  found  in  Virginia,  Vermont, 
New  Hampshire,  and  probably  in  Maine.  Kentucky,  therefore, 
contains  the  western  limit  of  the  distribution  of  this  insect, 
though  we  may  expect  that  soon  adjoining  states  may  become 
infested.  The  insect  exhibits  a  marked  tendency  to  spread 
farther  along  river  valleys  than  over  mountains,  and  is  dis- 
tinctly a  pest  of  city  and  village  trees  rather  than  of  trees  in  the 
open  fields  and  roadsides  of  the  country. 


Fig.  2. — Cluster  of  eggs,  greatly  enlarged. 


LIFE    HISTORY    AND    HABITS. 

The  overwintering  beetles  come  out  of  their  winter  quarters 
during  the  warm  days  of  early  spring,  mate,  and  as  soon  as 
the  leaves  unfold  they  begin  to  eat  small  rotuid  or  oval-shaped 
holes  through  them.  Many  leaves  are  thus  riddled  as  though 
shot  had  been  sent  through  them,  and  appear  like  the  illustra- 
tion on  the  front  page  of  this  bulletin. 

During  the  latter  part  of  May  and  early  in  June  the  females 
deposit  small  clusters  of  yellow  eggs  on  the  under  sides  of  the 
leaves.  The  period  of  ovipositing  extends  over  about  four 
weeks,  and  each  female  may  lay  five  or  six  hundred  eggs.     In 


6  CONNECTICUT    liXTKRIMIiXT    STATION    BULLETIN     1 55. 

about  a  week  the  eggs  hatch  and  the  young  larvae  or  grubs 
feed  upon  the  under  surface  of  the  leaves,  eating  off  the  green 
tissue  between  the  veins  and  leaving  the  veins  and  the  upper 
epidermis,  as  is  shown  in  Fig.  i. 

In  about  three  weeks  the  larvae  or  grubs  are  fully  grown, 
and  crawl  down  the  trunks  of  the  trees  or  drop  from  the  ends 
of  the  branches  to  the  ground  and  transform  to  the  naked  pupa 
stage.  The  great  proportion  of  the  pupae  are  found  close 
around  the  base  of  the  tree  or  lodged  in  the  crevices  of  the 
rough  bark  of  the  trunk  and  larger  branches.     Except  for  being 


t    • 


I  i 


Fig.  3. — Larvae  and  pupae,  twice  natural  size. 


in  crevices,  they  are  unprotected.  The  writer  has  seen  trees  in 
New  Haven  where  it  would  be  possible  to  gather  several  quarts 
of  these  pupae  at  the  base  of  a  single  tree. 

The  pupa  stage  lasts  about  ten  days,  then  the  adult  beetles 
appear,  and  lay  eggs  for  the  second  generation,  which  seldom 
does  much  harm  in  Connecticut.  Those  emerging  late  prob- 
ably do  not  lay  eggs  for  a  second  brood,  but  may  be  seen  crawl- 
ing and  flying  about  for  a  time,  feeding  more  or  less,  but 
early  going  into  winter  quarters,  usually  in  church  belfries, 
attics  of  houses,  barns,  sheds  or  other  out-buildings.  They 
also  pass  the  winter  in  cracks  of  fences,  telephone  poles,  or 
under  the  edges  of  the  loose  bark  of  the  trees.  In  some  of  the 
cities  worst  infested  the  adults  sometimes  gather  in  church  bel- 
fries in  such  numbers  that  they  can  be  swept  up  liy  the  half 


THE   ELM    LEAF   BEETLE.  7 

bushel.  The  ehii  leaf  beetle  often  occurs  with  the  two-spotted 
lady  beetle  in  dwellings,  simply  because  they  both  seek  the  same 
kind  of  a  place  for  hibernation.  Correspondents  frequently  send 
both  species  to  the  writer  and  desire  to  know  if  they  are  not 
in  some  way  responsible  for  the  injuries  to  their  carpets.  There 
is,  of  course,  no  relationship  or  similarity  in  food  habits  of  the 
three  species.  The  lady  beetle  is  predatory,  and  in  the  larval 
stage  destroys  numbers  of  plant  lice,  and  therefore  should 
never  be  destroyed.  The  elm  leaf  beetles  should,  of  course,  be 
killed  wherever  they  are  found. 

DESCRIPTION. 

The  eggs  are  bright  yellow  in  color,  bottle-shaped,  and 
resemble  the  eggs  of  the  Colorado  potato  beetle,  but  are  smaller. 
They  are  fastened  vertically  to  the  under  side  of  the  leaf  in 
clusters  of  from  five  to  twenty-five  arranged  in  two  or  three 
irregular  rows. 

When  first  hatched,  the  larva  is  dark  or  nearly  black,  covered 
with  tubercles  bearing  black  hairs.  As  the  larva  increases  in 
size  it  molts  several  times  and  on' becoming  full-grown  is  about 
one-half  inch  long,  dull  yellow  in  color,  with  a  pair  of  longi- 
tudinal black  stripes  along  the  back.  Head,  legs,  lateral  tuber- 
cles and  two  rows  of  small  tubercles  between  the  dorsal  stripes 
are  black.     The  tubercles  also  bear  black  hairs. 

The  pupa  is  about  one-fourth  inch  in  length  and  bright 
orange  yellow  in  color,  with  black  hairs  or  spines.  It  is  not 
enclosed  in  an  earthen  shell  to  protect  it,  but  is  found  at  the 
base  of  the  tree  perfectly  naked  and  wholly  unprotected. 

The  adult  beetle  is  light  yel- 
low in  color  when  it  first 
emerges,  but  soon  takes  on  a 
duller  hue,  and  finally  becomes 
a  dull  olive  green.  An  indis- 
tinct black  stripe  extends  from 
the  base  to  the  extremity  of 
Fig.  4.— Adult  beetles,  twice  each  wing  cover  just  inside  of 
natural  size.  j-j^g  margin.     Small  black  spots 

or  markings  on  the  pronotum  of  the  thorax  vary  greatly  in  size 
and  shape.     Legs  and  antennae  are  yellow. 


8  CONNECTICUT    EXPKRI.M  KXT    STATION    BULLETIN    I55. 

EFFECT    UPON    THE   TREES. 

It  has  previously  been  mentioned  that  the  adult  beetles  do 
more  or  less  feeding,  always  eating  holes  entirely  through  the 
leaves,  as  is  shown  on  cover  of  this  bulletin.  This  of  course 
injures  the  tree,  but  is  much  less  seri(nis  than  the  damage 
caused  by  the  larvae,  which  eat  away  the  under  surface  of  the 
leaves.  The  larvae  are  always  more  abundant  than  the  adult 
beetles,  and  are  more  voracious  in  their  feeding  habits.  The 
worst  infested  trees  usually  drop  their  leaves  in  Connecticut 
about  the  middle  of  Jul}-.  If  this  happens,  and  is  followed  by 
a  rainy  season,  new  leaves  will  be  put  out,  but  in  a  season  of  a 
protracted  drought  the  trees  may  fail  to  put  forth  new  leaves. 
In  either  case  the  tree  is  undoubtedly  weakened,  and  often  seri- 
ously so.  Sometimes  the  second  crop  of  leaves  is  devoured  by  the 
second  generation  of  beetles,  but  in  Connecticut  the  white  fungus 
mentioned  in  another  part  of  this  bulletin  is  apt  to  serve  as  an 
important  check  to  the  beetle  in  a  wet  season.  Two  complete 
defoliations,  one  succeeding  the  other,  usually  kill  a  tree. 
Usually,  however,  the  defoliation  is  not  quite  complete,  and  the 
trees  continue  to  exist  in  a  greatly  Aveakened  and  devitalized 
condition.  In  the  cities  and  larger  towns,  on  account  of  further 
injuries'"  by  horses,  by  leaky  gas  pipes  in  the  ground,  and  pave- 
ments which  cut  off  the  supply  of  moisture,  many  trees  have 
died.  In  1901  the  writer  was  called  to  Norwich,  where  nearly 
every  elm  had  died  for  a  distance  of  atout  one  and  one-half 
miles  on  a  prominent  residential  street.  These  trees  had  been 
weakened  by  the  constant  attacks  of  the  beetle  year  after  year, 
and  a  leaky  gas  main  finally  destroyed  what  little  vitalit)' 
remained.     Most  of  the  maple  trees  along  the  street  survived. 

In  many  cases  young  or  newly  planted  trees  seem  to  be 
especially  subject  to  attack,  and  therefore  should  receive  extra 
attention. 

FOOD  PLANTS. 

Elms  constitute  the  only  food  plants  knt^wn  for  this  insect, 
and  the  European  species  suffer  more  than  ilic  American  ones. 
The  English  elm   (  il  lit  us  ctiiiipcstris)   and  its  weeping  variety 


*  For  a  discussion  of  these  injuries  the  reader  should  consuU  I'uUetin 
131  of  this  Station. 


THE   ELM   LEAF   BEETLE.  9 

known  as  the  Camperdown  elm  are  favorites  of  the  beetle.  The 
writer  has  seen  these  trees  entirely  defoliated  in  New  Haven 
when  the  common  white,  or  American  elms,  were  uninjured. 
The  American  elm  is,  however,  the  next  choice,  followed  by  the 
Scotch  elm  {U.  montana),  and  though  no  variety  is  wholly 
exempt  from  attack,  the  winged  elm  (U.  alata),  the  slippery 
elm  {U.  fulva),  the  cork  elm  (U.  suhcrosa)  and  the  rock  elm 
{U.  raceiiiosa)  are  much  less  frequently  attacked. 

NUMBER  OF   GENERATIONS. 

According  to  Burgess,*  "in  New  Jersey,  Professor  J.  E. 
Smith  has  recorded  only  a  single  brood  and  sometimes  a  partial 
second  brood,  while  in  the  latitude  of  Washington,  D.  C, 
according  to  the  observations  of  Messrs.  Riley,  Howard  and 
Marlatt,  of  the  Division  of  Entomology,  two  annual  broods  and 
sometimes  a  partial  third  brood  have  been  found." 

Dr.  E.  P.  Felt,  State  entomologist,  of  Albany,  N.  Y.,  findsf 
two  well  marked  broods  and  a  partial  third  brood  at  Albany 
and  Troy,  N.  Y. 

The  writer  has  not  followed  out  this  matter  carefully  in 
Connecticut,  but  all  stages  are  found  on  the  trees  during  the 
first  half  of  September,  so  presumably  there  are  at  least  two 
broods,  but  the  egg-laying  period  of  the  adults  is  so  prolonged 
that  the  lines  of  demarcation  are  nearly  obliterated.  In  Con- 
necticut the  leaves  of  the  trees  severely  attacked  by  the  first 
brood  generally  turn  brown  and  drop  about  the  middle  of  July, 
when  the  larvae  are  descending  the  trees  to  pupate. 

NATURAL    ENEMIES. 

One  of  the  most  important  natural  enemies  of  the  elm  leaf 
beetle  in  Connecticut  is  a  fungus  known  to  botanists  as  Sporo- 
trichnm  globiiliferiiiii  Speg.  {S.  entoinopliUnm  Peck),  which 
attacks  the  pupae  and  adults  in  late  summer,  especially  in  a 
moist  season.  In  1902  this  fungus  was  prevalent,  and  the  fol- 
lowing season  the  elm  leaf  beetle  did  little  damage  to  the  trees. 
In  1906  the  beetles  were  abundant,  but  as  the  month  of  July  was 


*  Bulletin  No.  4,  page  17,  Ohio  Dept.  of  Agriculture,  Div.  of  Nursery 
and  Orchard  Inspection.     1905. 
t   Bulletin  No.  57,  N.  Y.  State  Museum,  p.  14,  1902. 


lO  COXXECTICUT    KXriiRI.MKXT    STATIOX    IJL'LLKTIX     I55. 

wet,  the  functus  developed  and  killed  a  great  many  beetles. 
Beetles  attacked  by  this  fungus  are  covered  with  white  mold, 
as  shown  in  Fig.  5. 

Predatory  bugs  of  at  least  three  species  of  the  genus  Podisus 
feed  upon  the  larvae  and  pupae,  and  Riley*  records  three 
species  of  beetles  that  also  devour  full-grown  larvae  and  pupae. 
The  praying  mantis  {Stagmomantis  Carolina  Linn.)  is  also  an 
enemy  of  the  elm  leaf  beetle  in  the  southern  portion  of  its 
ranee. 


Fig.   5. — Pupae  and   adults  killed  b}-   fungus.     Healthy   specimens   at 
the   left,   natural   size. 


REMEDIES. 

Spraying  zvith  poison.  Covering  the  foliage  with  some 
arsenical  poison  is  the  only  sure  means  of  preventing  injury  to 
the  trees,  and  for  this  purpose  arsenate  of  lead  is  unquestionabl\- 
the  most  satisfactory  of  these  poisons.  It  remains  better  in 
suspension  and  adheres  to  the  foliage  longer  than  Paris  green 
or  London  purple,  and  is  less  liable  to  injure  it.  As  there  are 
now  several  brands  of  good  arsenate  of  lead  on  the  market,  it 


*  Div.  of  Fntomolotiv,  U.  S.  Dcpt.  of  Agriculture,  Bulletins  Xo.  6,  p. 
10  and  No.  10,  p.  i.v 


THE   ELM   LEAF   BEETLE.  II 

will  no  longer  pay  to  make  it  up  each  time  from  lead  acetate 
and  arsenate  of  soda.  The  arsenate  of  lead  made  by  the  Merri- 
mac  Chemical  Co.,  Boston,  Mass. ;  Schoonmaker  &  Son,  Cedar 
Hill-on-Hudson,  N.  Y.,  and  the  Bowker  Insecticide  Co.,  Boston, 
Mass.,  (Disparene)  have  all  been  used  in  our  tests  and  have 
given  satisfaction.  Arsenate  of  lead  should  be  used  in  the 
following  proportions : — 

T^  ,     I  Arsenate  of  lead 3-S  lbs. 

Formula^  ,,,  ^  ^ 

(^  Water 50  gals. 

There  are  two  methods  of  spraying  elms:  (i)  To  spray  as 
soon  as  the  leaves  unfold,  the  treatment  being  aimed  especially 
at  the  parent  beetles,  and  to  forestall  all  injury.  As  growth 
■takes  place,  new  leaves  are  constantly  appearing,  and  these  will 
not  carry  poison  unless  the  application  is  from  time  to  time 
repeated.  This  should  be  done  often  enough  to  'keep 
the  foliage  well  coated  with  poison  until  July  ist,  when  growth 
usually  ceases,  and  both  sides  of  the  leaves  should  be  coated. 

(2)  The  other  method  is  to  spray  the  under  sides  of  the 
leaves  very  thoroughly  about  June  ist,  or  soon  after  the  eggs 
begin  to  hatch.  This  treatment  is  aimed  at  the  larvae,  and 
sometimes  a  single  spraying  is  sufficient,  as  the  poison  will 
remain  throughout  the  season.  By  it  the  great  bulk  of  damage 
will  be  prevented,  but  the  leaves  will  show  the  small  holes  made 
by  the  parent  beetles  before  the  poison  was  applied. 

If  arsenate  of  lead  cannot  be  procured  and  it  seems  desirable 
to  use  other  poisons,  Paris  green  can  be  substituted. 

This  should  be  used  at  the  following  rate : 

r  Paris  Green i  lb. 

Formula-]  Fresh  lime 3  lbs. 

[  Water 50  gals. 

Paris  green  is  cjuicker  in  its  action  upon  the  insects  than 
arsenate  of  lead,  but  will  not  remain  as  long  upon  the  trees. 
Unless  the  lime  is  added,  there  is  danger  of  "burning"  the 
leaves.    Lime  is  not  needed  with  arsenate  of  lead. 

The  cost  of  spraying  elm  trees  will  var}^  from  ten  cents 
each  in  case  of  small  trees  to  five  dollars  or  more  for  the  largest 
trees,  according  to  the  price  of  labor  and  the  efficiency  of  the 
outfit. 


12  CONNECTICUT    EXPERIMKXT    STATION    HLTJ.ETIN     I55. 

DcstroxiiiL!;  the  piipac.  Tf  the  trees  have  not  been  protected 
by  spraying-,  and  have  been  attacked  and  injured  by  a  horde 
of  beetles  and  their  larvae,  it  is  always  advisable  to  destroy  the 
insects  in  the  pupa  stage  at  the  base  of  the  trees,  in  order  to 
reduce  the  crop  for  next  year  as  much  as  possible.  These  can 
often  be  swept  up  in  large  quantites  ;  they  can  be  killed  by 
sprinkling  them  with  hot  water ;  but  best  of  all  is  to  spray  the 
ground  not  only  close  to  the  tree  but  as  far  away  as  the  branches 
reach,  and  also  spray  the  bark  of  the  trunk  and  large  branches, 
with  kerosene  emulsion  or  some  other  contact  insecticide.  The 
pupae  are  easy  to  kill,  but  as  they  remain  in  the  pupa  stage  only 
about  ten  days,  it  is  essential  that  this  work  be  done  at  the  right 
time,  and  it  is  only  when  we  observe  that  most  of  the  larvae 
descending  the  trunk  have  transformed  to  bright  yellow  pupae 
that  we  can  know  Avhen  is  the  proper  time  to  act. 

Destroying  the  adult  beetles.  The  beetles  should  of  course 
be  destroyed  in  attics,  belfries  and  other  places  where  they 
hibernate.  This  can  best  be  done  by  sweeping  them  up  before 
they  become  very  active  in  spring  and  dropping  them  into  the 
fire,  hot  water  or  kerosene  to  kill  them. 

OUTFIT  FOR  SPRAYING  ELM  TREES. 

The  barrel  hand-power  pump  can  be  used  for  spraying  small 
trees  or  for  a  limited  number  of  large  trees,  but  if  one  expects 
to  make  a  business  of  spraying  street  trees,  it  will  pay  to  pro- 
cure a  power  sprayer ;  this  may  be  a  steam  or  gasoline  engine 
with  pump,  or  Avhat  is  perhaps  better,  the  "X'iagara  Gas 
Sprayer,"  which  utilizes  cylinders  of  carbonic  acid  gas  to 
furnish  pressure,  thus  doing  away  with  a  pump.  Each  large 
village  and  city  should  have  at  least  one  power  sprayer  that  can 
be  put  to  immediate  use  for  spraying  street  c^r  park  trees. 
Strong  one-half  inch  hose  should  be  provided  in  long  lines  of 
from  fifty  to  two  hundred  feet,  and  from  four  to  six  of  these 
can  be  attached  to  each  power  sprayer.  Even  a  larger  number 
might  be  attached,  but  while  in  operation  some  workmen  would 
be  in  the  way  of  others,  so  that  nothing  wmild  be  gaincil.  Mr. 
H.  L.  Frost  of  Boston,  who  is  in  the  spraying  business, 
informed  the  writer  that  four  linos  of  hose  is  al>^ut  tlie  most 
economical  number  for  each  outfit.  Each  hose  is  turnisliod 
with    an    extension    rod    with    closing   val\-c    at    the    lower    end 


THE   ELM    LEAF   BEETLE.  1 3 

and  a  cluster  of  nozzles  at  the  upper  end.  These  rods  should 
be  of  different  lengths,  from  four  to  twelve  or  fOiUrteen  feet  for 
the  different  kinds  of  work.  Any  of  the  standard  nozzles  such 
as  "A/^ermorel,"  "Mistr}^,"  or  "Spra3'motor"  will  be  found 
satisfactory,  and  if  several  are  used  together  in  a  cluster  one 
is  able  to  cover  more  leaf  surface  in  a  given  time. 

For  getting  about  in  tall  trees  it  will  be  necessary  for  the  men 
to  be  provided  with  climbing  irons  and  extension  ladders. 

SUMMARY. 

The  elm  leaf  beetle  was  introduced  into  this  country  from 
Europe  about  seventy  years  ago,  and  caused  serious  injury  to 
trees  at  Baltimore,  Md.,  in  1838  and  1839.  From  this  point  it 
spread  slowly,  chiefly  to  the  northward,  reaching  Connecticut 
in  the  early  nineties,  and  injuring  and  killing  many  fine  old  trees 
in  the  coast  towns.  Later,  inland  towns  were  attacked,  and  the 
trees  ravaged.  The  insect  is  now  found  from  Charlotte,  N.  C, 
as  far  north  as  North  Conway,  N.  H.,  and  as  far  west  as  central 
Kentucky,  but  has  not  proven  destructive  to  elm  trees  north 
of  Massachusetts.  It  is  preeminently  a  pest  of  shade  trees  in 
cities  and  towns,  and  seldom  injures  trees  in  the  open  fields. 
Since  1896  the  attacks  have  diminished,  but  the  pest  was  again 
serious  in  1906. 

The  winter  is  passed  by  the  adult  beetles  in  attics,  belfries 
and  cracks  in  fences,  and  they  come  forth  in  April,  and  later 
feed  and  lay  their  yellow  eggs  upon  the  unfolding  leaves. 
Beetles  eat  holes  through  the  leaves,  eggs  hatch  in  a  week,  and 
the  larvae  eat  off  the  green  tissue  from  the  under  surface,  caus- 
ing the  leaves  to  turn  brown  and  fall  about  the  middle  of  July, 
at  Avhich  time  the  larvae  are  about  full  grown.  Then  they 
descend  to  the  base  of  the  tree  and  transform  to  naked  pupae; 
ten  days  later  the  adult  beetles  emerge  and  lay  eggs  for  the 
second  brood  or  go  early  into  winter  quarters. 

Two  complete  defoliations  in  succession  will  kill  a  tree. 

Hoiv  to  Fight  the  Elm  Leaf  Beetle. 

(i)  Search  all  attics,  church  belfries  and  cupolas  for  the 
dormant  beetles  in  winter  and  early  spring.  Sweep  them  up 
and  burn  them. 


14         CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I55. 

(2)  Spray  the  leaves  with  poison  as  soon  as  they  have 
opened,  if  their  shot-hole  appearance  shows  that  the  beetles  are 
there  in  abundance,  and  the  under  sides  of  the  leaves  should  be 
coated  about  June  ist  to  destroy  the  larvae  or  grubs. 

(3)  When,  later  in  the  season,  the  yellow  pupae  appear  on 
the  trunks  of  trees  and  the  ground  beneath,  kill  them  with  a 
spray  of  kerosene  emulsion  or  by  sweeping  them  up  and  Ijurn- 
ing  or  soaking  with  kerosene. 

The  first  and  third  measures  should  be  taken  by  each  house- 
holder, church  or  social  organization,  at  individual  expense. 
The  spraying,  which  is  difficult  and  expensive  if  the  trees  are 
large,  can  only  be  done  by  concerted  action  of  the  town  or 
borough  authorities.  For  extensive  spraying  work  power 
sprayers  are  desirable,  but  small  elms  or  a  few  large  trees  can 
be  treated  successfully  by  means  of  a  hand  pump  of  barrel  size. 
The  "Niagara  gas  sprayer"  in  operation  is  shown  in  Fig.  6. 


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